[recovery] Added option to forward opt

[ljharb]

https://web.archive.org/web/20201110211130/https://github.com/substack/subarg/pull/6

filed by @tornqvist

I'm using subarg as a way of nesting commands for one and the same program and as so only running the top level context through minimist with options leaves all subargs without their aliases, in my case.

This PR adds the option forward which, if set to something truthy, will keep forwarding the minimist opts to every nested context.